A blood pressure is one index for analyzing a circulatory disease. Performing risk analysis based on the blood pressure is effective in preventing cardiovascular diseases such as stroke, heart failure, and cardiac infarction. Conventionally, diagnosis is made from the blood pressure (examination room blood pressure) measured in medical institutions such as at the time of hospital visits, health checks, or the like. However, it is found from researches of recent years that the blood pressure (home blood pressure) measured at home is more useful in the diagnosis of circulatory diseases than the examination room blood pressure. Accompanied therewith, over 30 million sphygmomanometers for use at home are widely used in the country.
In the conventional blood pressure measurement device, the cuff is wrapped around the measurement site of a living body in advance for blood pressure measurement, but it is difficult to define the appropriate wrapping strength because the extent of the wrapping strength, that is, pressurization of the wrapping on the living body is not known. Accordingly, patent document 1 (Japanese Unexamined Patent Publication No. 2005-305028 (Japanese Patent No. 3815487) describes a configuration of enclosing gas in the cuff in advance, and then automatically wrapping the cuff around the measurement site. Whether or not relative displacement of the pressure in the cuff in the process of wrapping around the measurement site reaches a predetermined level is detected to detect if the wrapping state is in an appropriate state for blood pressure measurement.
In patent document 2 (Japanese Unexamined Patent Publication No. 6-319707), the cuff compliance obtained from the relationship of the pressure in the cuff and the change in volume after wrapping the cuff around the measurement site is used to correct the amplitude of the pulse wave used in the blood pressure measurement process, so that highly accurate blood pressure measurement can be carried out without depending on the person to be measured or the wrapping strength of the cuff.
The sphygmomanometer of patent document 3 (Japanese Unexamined Patent Publication No. 2-114934) and patent document 4 (Japanese Patent Publication No. 4134234) starts the blood pressure measurement with the cuff wrapped around the measurement site, and determines the attachment state of the cuff with respect to the measurement site based only on the amount of change of the subsequent cuff pressure. Therefore, this procedure can also be applied to the blood pressure measurement device having a configuration in which the person to be measured wraps the cuff around the measurement site.